i have a 305 tbi in a 92 rs. im planning a rebuild, but i dont know how to go about doing it. i already know i want flat top pistons, and the main problem is the throttle body. i heard one off of a 454 would bolt right up to mine and replace my current one and im wondering if this is true? please help me, and any other suggestions would be appreciated. btw i am not going to do a swap or get it bored and/or stroked. so please dont pester me with those suggestions.

NO 454 tbi...its waaay too much trouble...
Upgrade the cam...upgrade the heads if its in the budget...visit tbichips.com for a new PROM and check this out

http://cgi.ebay.com/ebaymotors/454-3...Q5fAccessories

http://cgi.ebay.com/ebaymotors/NEW-G...Q5fAccessories

If you plan on rebuilding the engine a .010 or .020 in overbore will probably be mandatory. Though it depends of the condition of the cylinderbores. Same for milling the deck of the block, or you may end up with a bad quench.
Piston cc volume wil depend on head combustion chamber cc, to have the proper copression ratio.
Don get carried away too much with the TB, your stock one is ok for around 280fwhp.
Read the sticky post's on top of this forum, it will help you know your engine and make the right choices.

The 454 TBI has larger injectors so you will have to change the tune for it to run right.